Up to 250 offices face closure and 25,000 jobs lost by 2011, leaving staff having to work overtime or see consultants hired to mask the impact of the cuts, said the union.

PCS general secretary, Mark Serwotka, said: “It is lunacy for HMRC to plough ahead with closing more than 250 offices and cutting a further 12,500 jobs by 2011.

“As HMRC’s own staff survey indicates, morale is dangerously low. These are some of the most loyal staff, responsible for collecting taxes to build schools and hospitals, securing our borders and overseeing the payment of tax credits.”

An HMRC spokesman told The Guardian: “We have invited the trade unions to talks and asked them to suspend their strike ballot while these talks take place.”

The ballot is expected to close on 23 January with result announced shortly afterwards.